Hi!,
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Its not very clear as to what you have ,kindly mention how the lesion looks like .Is it a pimple which has become big and not healing ,or is it a small raised shiny lesion.How long you have been having this .Have you taken any treatment.
kindly also mention your age and gender.

Usually what we see on chin is pimples and that can be because of various reasons .A wrong selection of soap , use of moisturizers ,hormonal disturbance ,oily skin etc can all lead to pimples .
You can use clindamycin gel to adaferin gel over the lesions.If this doesn't help then you would require oral antibiotics or hormonal medicines .
You should also use a anti acne face wash twice a day.

Kindly reply with the answers so that I can help you further.

regards,
Dr.Bharat chawda